drm/ast: Call drm_atomic_helper_check_plane_state() unconditionally

Always call drm_atomic_helper_check_plane_state() in each plane's
atomic_check function. At the minimum, it needs to set or clear the
plane state's 'visible' field. Otherwise the plane-state handling
is bogus and would keep updating planes that have been disabled.

While at it, also warn if the primary plane has been enabled, but is
not visible. This cannot legally happen as the plane always covers
the entire screen.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Tested-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221013112923.769-3-tzimmermann@suse.de